This invention relates to the production of reclosable bags which have a reclosable seal formed by releasable and engagable zipper strips attached to opposed walls of the bag.
The reclosable seal is often provided adjacent a nonreclosable seal, for example a heat seal, and allows the bag to be reclosed with the non-reclosable seal has been opened. Such bags are often formed by use of a horizontal or a vertical form-fill-seal machine.
In preparing continuous web material for supply to a form-fill-seal machine, or other apparatus for forming bags having reclosable seals, a continuous length of web material from which the bags are to be formed is advanced in a longitudinal direction and separate lengths of zipper strip are applied to the web so that they are at spaced intervals longitudinally of the web and extend transversely (usually perpendicularly) to the longitudinal direction. Each zipper strip length comprises first and second interengagable profiles which are pre-assembled into at least partial engagement with each other. This is known as “cross-web technology”: see our published UK patent application GB-A-2349603 which describes a form-fill-seal machine using that technology and the entire contents of which are incorporated herein by reference. FIG. 5 of GB-A-2349603 shows the use of a pair of spring-loaded zipper sealing jaws which operate to seal the zipper strips to the walls of the bag simultaneously with formation of the non-reclosable end seal of the bag. This operation requires a certain time as it is necessary for the zipper sealing jaws to supply heat to the zipper strips to seal them to the bag walls. The steptherefore slows down the entire form-fill-seal operation.